1. Field of the Invention
The present invention relates to a light-emitting module provided with a light-emitting element in a sealed space, and a method for manufacturing the light-emitting module.
2. Description of the Related Art
A light-emitting element, in which a layer containing a light-emitting compound formed in a film shape is provided between a pair of electrodes, is known. Examples of such a light-emitting element include an organic EL element (also referred to as an organic electroluminescence element) and an inorganic EL element. In the organic EL element, light emission can be obtained from a layer containing a light-emitting organic compound when voltage is applied between a pair of electrodes. In recent years, research and development have been extensively conducted on light-emitting devices (specifically, lighting devices and display devices) including organic EL elements.
In an organic EL element, light is emitted from a layer containing a light-emitting organic compound. The layer containing a light-emitting organic compound has a higher refractive index than the air. Light emitted from the layer having a higher refractive index than the air is difficult to extract to the air; thus, special contrivance is needed so as to efficiently extract the light from the organic EL element to the air.
For example, an organic electroluminescence element disclosed in Patent Document 1 is an organic electroluminescence device in which a back electrode, an organic electroluminescence light-emitting layer, and a light-transmitting front electrode are stacked in this order. In the organic electroluminescence element, the back electrode is a light-transmitting electrode, and a light-scattering layer having a high refractive index, which includes a material having a refractive index of 80% or more of that of the organic electroluminescence light-emitting layer as its main component, is provided on a back side of the back electrode. Further, the refractive index of a layer provided between the light-emitting layer and the light-scattering layer having a high refractive index is adjusted so that 40% or more of light emitted from the light-emitting layer to the back side enters the light-scattering layer having a high refractive index.
A dispersion electroluminescence element disclosed in patent document 2 is provided with a light-scattering back-face sheet. With such a structure, extraction efficiency of light to the outside is enhanced. Note that the dispersion electroluminescence element is one mode of an inorganic EL element.
The reliability of an organic EL element tends to decrease in the environment where there are impurities (such as water and/or oxygen) in the air. A variety of structures for sealing the organic EL element have been developed. For example, a sealing structure in which an organic EL element formed over a substrate with low moisture permeability is covered with a sealing film with low moisture permeability is known.